Cu-be base amorphous alloy

ABSTRACT

The present invention provides a Cu—Be based amorphous alloy comprising an amorphous phase of 50% or more by volume fraction. This alloy has a composition represented by the following formula: Cu 100-a-b Be a (Zr 1-x-y Hf x Ti y ) b . In the formula, “a and “b” represent atomic percentages which are 0&lt;a≦20 and 20≦b≦40, and “x” and “y” represent atomic fractions which are 0≦x≦1 and 0≦y≦0.8. The alloy may contain a small amount of one or more elements selected from the group consisting of Fe, Cr, Mn, Ni, Co, Nb, Mo, W, Sn, Al, Ta and rare-earth elements and/or the group consisting of Ag, Pd, Pt and Au. The alloy has a wide supercooled-liquid temperature range and a large reduced glass transition temperature (Tg/Tm) to achieve a high thermal stability against crystallization or a high glass-forming ability.

FIELD OF THE INVENTION

[0001] The present invention relates to a Cu—Be based amorphous alloyhaving a high glass-forming ability, enhanced mechanical properties andan excellent workability.

BACKGROUND OF THE INVENTION

[0002] A Cu—Be alloy is formed by adding beryllium to copper so as toprovide a Cu based alloy having age-hardening properties. While a Cu—Bealloy containing 2% of Be has a relatively low tensile strength of about0.5 GPa just after a solution heat treatment, the strength will beincreased up to 1.5 GPa through age hardening. By taking advantages ofits age-hardening properties and excellent corrosion resistance, theCu—Be alloy containing 2% of Be is widely used as high-performance andhigh-reliability springs in various fields such as electronic industriesand telecommunication equipment industries. It can also be used as othervarious products such as molding dies for plastic materials and safetymachine tools free from spark caused by a mechanical impact. A Cu—Bealloy containing 1% or less of Be is used to utilize its high electricconductivity.

[0003] Heretofore, particular alloys such as Fe-based, Co-based andNi-based alloys have been able to be formed in an amorphous phase toobtain an excellent strength, elasticity and corrosion resistancesuperior to those in its crystalline phase. It has also been known thatthe amorphous alloys exhibit excellent superplastic-forming propertiesin a supercooled liquid temperature range.

[0004] As an amorphous alloy containing a relatively large amount of Cu,there has been known a glassy alloy containing Zr, Ti, Cu and Ni, whichis disclosed in domestic republication of PCT international publicationfor patent applications Nos. JP10-512014 and JP8-508545. In thiscontext, the inventors have achieved an invention of an improvedCu-based amorphous alloy and applied for a patent (Japanese PatentApplication No. 2000-397007).

[0005] The conventional Cu—Be crystalline alloy can be formed into abulk alloy but with a lower strength than that of an amorphous alloy.Besides, a viscous-flow-like superplastic forming cannot be applied tosuch a Cu—Be crystalline alloy. On the other hand, it has been knownthat in a heating process, a particular amorphous alloy exhibits asupercooled liquid phase allowing the viscous-flow-like superplasticforming, before the initiation of crystallization. In this temperaturerange allowing the formation of the supercooled liquid phase, theamorphous alloy can be formed into a product having any desired shapethrough a plastic forming. Further, an alloy having a high glass-formingability can be formed as a bulk amorphous alloy through a copper-moldcasting method.

SUMMARY OF THE INVENTION

[0006] It is therefore an object of the present invention to provide aCu—Be based amorphous alloy with an amorphous-phase volume fraction of50% or more, having a wide supercooled-liquid temperature range and ahigh reduced-glass transition temperature (Tg/Tm) to exhibit a highthermal stability against crystallization so as to obtain a highglass-forming ability, enhanced mechanical properties, and excellentworkability or working properties.

[0007] In order to achieve the above object, the inventors maderesearches for the purpose of providing a metallic glass materialcapable of forming a bulk metallic glass therefrom. In result, theinventors have found out that a Cu—Be—Zr—Ti—Hf based alloy can exhibit asupercooled liquid temperature range of 25 K or more to provide a Cu—Bebased amorphous alloy, e.g. a Cu—Be based amorphous alloy bar having adiameter (thickness) of 1 mm or more, having a high glass-formingability, high strength, high elasticity and excellent workability, andfinally accomplished the present invention.

[0008] Specifically, according a first aspect of the present invention,there is provided a Cu—Be based amorphous alloy comprising an amorphousphase of 50% or more by volume fraction. This alloy has a compositionrepresented by the following formula:Cu_(100-a-b)Be_(a)(Zr_(1-x-y)Hf_(x)Ti_(y))_(b). In the formula, “a” and“b” represent atomic percentages which are 0<a≦20 and 20≦b≦40, and “x”and “y” represent atomic fractions which are 0≦x≦1 and 0≦y≦

[0009] According a second aspect of the present invention, there isprovided a Cu—Be based amorphous alloy comprising an amorphous phase of50% or more by volume fraction. This alloy has a composition representedby the following formula:Cu_(100-a-b)Be_(a)(Zr_(1-x-y)Hf_(x)Ti_(y))_(b)In the formula, “a” and“b” represent atomic percentages which are 5<a≦10 and 30≦b≦40, and “x”and “y” represent atomic fractions which are 0≦x≦1 and 0≦y≦

[0010] According a third aspect of the present invention, there isprovided a Cu—Be based amorphous alloy comprising an amorphous phase of50% or more by volume fraction. This alloy has a composition representedby the following formula:Cu_(100-a-b-c-d)Be_(a)(Zr_(1-x-y)Hf_(x)Ti_(y))_(b)M_(c)T_(d). In theformula, M represents one or more elements selected from the groupconsisting of Fe, Cr, Mn, Ni, Co, Nb, Mo, W, Sn, Al, Ta and rare-earthelements; T represents one or more elements selected from the groupconsisting of Ag, Pd, Pt and Au; “a”, “b”, “c” and “d” represent atomicpercentages which are 0<a≦20, 20≦b≦40, 0<c≦5 and 0<d≦10; and “x” and “y”represent atomic fractions which are 0≦x≦1 and 0≦y≦0.8.

[0011] According a fourth aspect of the present invention, there isprovided a Cu—Be based amorphous alloy comprising an amorphous phase of50% or more by volume fraction. This alloy has a composition representedby the following formula:Cu_(100-a-b-c-d)Be_(a)(Zr_(1-x-y)Hf_(x)Ti_(y))_(b)M_(c)T_(d). In theformula, M represents one or more elements selected from the groupconsisting of Fe, Cr, Mn, Ni, Co, Nb, Mo, W, Sn, Al, Ta and rare-earthelements; T represents one or more elements selected from the groupconsisting of Ag, Pd, Pt and Au; “a”, “b”, “c” and “d” represent atomicpercentages which are 5<a≦10, 30≦b≦40, 0<c≦5 and 0<d≦10; and “x” and “y”represent atomic fractions which are 0≦x≦1 and 0≦y≦0.8.

[0012] When the alloy of the present invention was processed through acopper-mold casting method and subjected to a thermal analysis, a heatgeneration arising from a significant glass transition andcrystallization was observed. This analysis showed that a metallic glasscan be prepared by the copper-mold casting method.

[0013] A metallic glass ingot having a diameter (thickness) of 1.0 mm ormore can be prepared from the amorphous alloy of the present invention.If the alloy composition is out of the range defined in the presentinvention, the glass-forming ability will be deteriorated to facilitatethe creation and growth of crystal nuclei in the course ofsolidification from its molten state and form a mixture of glass andcrystalline phases. No glass phase or only a crystalline phase is formedin an alloy having a composition quite different from the range definedin the present invention.

[0014] The Cu—Be based amorphous alloy of the first to fourth aspects ofthe present invention may have a supercooled liquid temperature rangeΔTx of 25 K or more. This supercooled liquid temperature range ΔTx isrepresented by the following formula: ΔTx=Tx-Tg. In the formula, Txrepresents the crystallization initiation temperature of the alloy, andTg represents the glass transition temperature of the alloy.

[0015] Further, the alloy of the present invention may have a reducedglass transition temperature of 0.58 or higher. This reduced glasstransition temperature is represented by the following formula: Tg/Tm.In this formula, Tm represents the melting temperature of the alloy.

[0016] The alloy of the present invention has a large critical thicknessto be formed as an amorphous phase, and can be formed into a bar orplate material which includes an amorphous phase volume fraction of 50%or more, particularly 90% or more and has a diameter or thickness of 1mm or more, through a copper-mold casting process.

[0017] The term “supercooled liquid temperature range” herein means thedifference between a glass transition temperature of the alloy and acrystallization initiation temperature of the alloy, which aredetermined by a differential scanning calorimetry (DSC) performed at aheating rate of 40 K/minute. The “supercooled liquid temperature range”is a value indicative of resistibility against crystallization which isequivalent to thermal stability of amorphous state, glass-formingability or workability. The alloy of the present invention has asupercooled liquid temperature range of 25 K or more.

[0018] The term “reduced glass transition temperature” herein means aratio of the glass transition temperature (Tg) to a melting temperature(Tm) of the alloy, which is determined by a differential thermalanalysis (DTA) performed at a heating rate of 5 K/minute. The “reducedglass transition temperature” is a value indicative of the glass-formingability.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] One embodiment of the present invention will now be described.

[0020] A Cu—Be based amorphous alloy of the present invention comprisesfundamental elements of Zr, Hf and Ti. The atomic percentage of Zr is inthe range of zero to 40%, preferably 20 to 30%. The atomic percentage ofHf is in the range of zero to 40%, preferably 20 to 30%. The atomicpercentage of Ti is in the range of zero to 32%, preferably 10 to 20%.If the atomic percentage of Zr, Hf or Ti is out of the above range, nosupercooled liquid range will be exhibited and the value of Tg/Tm willbe 0.56 or lower, which leads to deteriorated glass-forming ability ofthe alloy.

[0021] The total atomic percentage of Zr, Hf and Ti is set in the rangeof 20 to 40%. If this total atomic percentage is less than 20% orgreater than 40%, the glass-forming ability will be deteriorated to formno bulk amorphous material. More preferably, the total atomic percentageof Zr, Hf and Ti is set in the range of 30 to 40%.

[0022] In the Cu—Be based amorphous alloy of the present invention, Beserves as an element for enhancing the glass-forming ability to providean increased strength in a resulting amorphous alloy. Be is added at anatomic percentage of 20% or less. If this atomic percentage is greaterthan 20%, the glass-forming ability will be deteriorated. Preferably,the atomic percentage of Be is set in the range of 5 to 10%.

[0023] A part of Cu may be substituted with a small amount of one ormore elements selected from the group consisting of Fe, Cr, Mn, Ni, Co,Nb, Mo, W, Sn, Al, Ta and rare-earth elements (Y, Gd, Tb, Dy, Sc, La,Ce, Pr, Nd, Sm, Eu and Ho). The addition of these elements caneffectively improve the mechanical strength of the alloy but causesdeterioration in the glass-forming ability. Thus, it is desired to addthese elements at the atomic percentage of 5% or less.

[0024] Further, a part of Cu may be substituted with one or moreelements selected from the group consisting of Ag, Pd, Au and Pt at anatomic percentage of 10% or less. The supercooled liquid temperaturerange can be slightly expanded by substituting Cu with these elements.However, if these elements are added at an atomic percentage of morethan 10%, the supercooled liquid temperature range will be less than 25K, resulting in deteriorated glass-forming ability.

[0025] The Cu—Be based amorphous alloy of the present invention can becooled and solidified from its molten state through any suitableconventional method such as a single-roll melt spinning method,twin-roll melt spinning method, in-rotating liquid spinning method oratomization method to provide an amorphous alloy in the form of aribbon, thin strip, filament, grain or powder. In addition, a highglass-forming ability of the Cu—Be based amorphous alloy of the presentinvention makes it possible to obtain a bulk amorphous alloy having anydesired shape through a copper-mold casting method, as well as the aboveconventional methods.

[0026] For example, in a typical copper-mold casting method, aftermelting a master alloy having the alloy composition defined in thepresent invention within a silica tube kept under argon atmosphere, themolten metal can be filled in a copper mold at an injection pressure of0.5 to 1.5 kg·f/cm² and solidified to obtain an amorphous alloy ingot.Alternatively, any other suitable method such as a high-pressuredie-casting method or a squeeze-casting method may be used.

(EXAMPLE)

[0027] Examples of the present invention will be described below. Foreach of materials as master alloys having alloy compositions in Table 1(Inventive Examples 1 to 14 and Comparative Examples 1 to 6) and Table 2(Inventive Examples 15 to 26, Comparative Examples 7 to 10), aftermelting the master alloy through an arc-melting method, a bar-shapedsample was prepared through a copper-mold casting method to determine acritical thickness for glass-formation. The amorphous phase of thebar-shaped sample was confirmed through an X-ray diffraction method. Acompression test piece was prepared, and the test piece was subjected toa compression test using an Instron-type testing machine to evaluate itscompressive fracture strength (σf). These evaluation results are shownin Tables 1 and 2. TABLE 1 Compressive Strength Critical (σ f) ThicknessAlloy Composition (MPa) (mm) Inventive Example 1Cu₅₇Zr_(28.5)Ti_(9.5)Be₅ 2350 5 Inventive Example 2 Cu₅₄Zr₂₇Ti₉Be₁₀ 24005 Inventive Example 3 Cu₅₁Zr_(25.5)Ti_(8.5)Be₁₅ 2300 1 Inventive Example4 Cu₄₈Zr₂₄Ti₈Be₂₀ 2350 1 Inventive Example 5 Cu₅₇Zr₂₈Ti₉Nb₁Be₅ 2300 5Inventive Example 6 Cu₅₇Zr₂₇Ti₉Nb₂Be₅ 2300 5 Inventive Example 7Cu₅₇Zr₂₈Ti₉Pd₁Be₅ 2300 5 Inventive Example 8 Cu₅₇Zr₁₉Ti₉Be₅ 2400 4Inventive Example 9 Cu₅₄Zr₁₈Ti₁₈Be₁₀ 2200 4 Inventive Example 10Cu₅₅Zr₂₈Ti_(9.5)Be_(7.5) 2400 5 Inventive Example 11 Cu₅₇Zr₃₈Be₅ 2200 2Inventive Example 12 Cu₅₇Zr₃₈Be₅ 2350 2 Inventive Example 13Cu₅₇Zr₂₈Ti₁₀Be₅ 2200 2 Inventive Example 14 Cu₅₇Hf₂₈Ti₁₀Be₅ 2300 2Comparative Example 1 Cu₆₀Zr₃₀Ti₁₀ 2115 4 Comparative Example 2Cu₆₀Hf₃₀Ti₁₀ 2143 4 Comparative Example 3 Cu₆₀Zr₂₀Ti₂₀ 2015 3Comparative Example 4 Cu₆₀Hf₂₀Ti₂₀ 2078 4 Comparative Example 5Cu₆₀Zr₁₅Hf₁₅Ti₁₀ 2100 3 Comparative Example 6 Cu₅₅Zr₂₅Ti₂₀ 1970 3

[0028] TABLE 2 Compressive Strength Critical (σ f) Thickness AlloyComposition (MPa) (mm) Inventive Cu₅₈Be₃Zr₁₇Hf₁₂Ti₈Fe₂ 2450 3 Example 15Inventive Cu₅₈Be₃Zr₁₇Hf₁₂Ti₈Cr₂ 2500 2 Example 16 InventiveCu₅₈Be₃Zr₁₇Hf₁₂Ti₈Mn₂ 2600 4 Example 17 Inventive Cu₅₈Be₃Zr₁₇Hf₁₂Ti₈Gd₂2400 2 Example 18 Inventive Cu₅₈Be₃Zr₁₇Hf₁₂Ti₈Nd₂ 2500 3 Example 19Inventive Cu₅₈Be₃Zr₁₇Hf₁₂Ti₈La₂ 2600 3 Example 20 InventiveCu₅₈Be₃Zr₁₇Hf₁₀Ti₈W₂Al₂ 2600 3 Example 21 InventiveCu₅₈Be₃Zr₁₇Hf₁₀Ti₈Ta₂Sn₂ 2610 3 Example 22 InventiveCu₅₈Be₃Zr₁₇Hf₁₀Ti₈Al₂Sn₂ 2500 3 Example 23 InventiveCu₅₈Be₃Zr₁₇Hf₁₀Ti₈Sc₂Pd₂ 2500 3 Example 24 InventiveCu₅₈Be₃Zr₁₇Hf₁₀Ti₈Sm₂Ag₂ 2660 3 Example 25 InventiveCu₅₈Be₃Zr₁₇Hf₁₀Ti₈Ho₂Au₂ 2570 3 Example 26 Comparative Cu₇₀Zr₂₀Ti₁₀ 0.5Example 7 Comparative Cu₇₀Hf₂₀Ti₁₀ 0.3 Example 8 ComparativeCu₇₀Zr₁₀Hf₁₀Ti₁₀ 0.5 Example 9 Comparative Cu₆₀Zr₄₀ 0.3 Example 10

[0029] As seen in Tables 1 and 2, the amorphous alloy containing Be ineach Inventive Example can be formed into an amorphous alloy bar whichhas a diameter of 1 mm or more, even 3 mm or more, and a compressivefracture strength (σf) of 2000 MPa or more.

Industrial Applicability

[0030] As mentioned above, a Cu—Be based amorphous alloy of the presentinvention makes it possible to facilitate the production of a bar-shapedsample having a diameter (thickness) of 1 mm or more through acopper-mold casting method. The obtained amorphous alloy exhibits asupercooled liquid temperature range ΔTx of 25 K or more, and has a highstrength. Thus, the present invention can provide a practically variableCu—Be based amorphous alloy having a high glass-forming ability,enhanced mechanical properties and excellent workability.

What is claimed is:
 1. A Cu—Be based amorphous alloy comprising anamorphous phase of 50% or more by volume fraction, said alloy having acomposition represented by the following formula:Cu_(100-a-b)Be_(a)(Zr_(1-x-y)Hf_(x)Ti_(y))_(b), wherein a and brepresent atomic percentages which are 0<a≦20 and 20≦b≦40, and x and yrepresent atomic fractions which are 0≦x≦1 and 0≦y≦0.8.
 2. A Cu—Be basedamorphous alloy comprising an amorphous phase of 50% or more by volumefraction, said alloy having a composition represented by the followingformula: Cu_(100-a-b)Be_(a)(Zr_(1-x-y)Hf_(x)Ti_(y))_(b), wherein a and brepresent atomic percentages which are 5<a≦10 and 30≦b≦40, and x and yrepresent atomic fractions which are 0≦x≦1 and 0≦y≦0.8.
 3. A Cu—Be basedamorphous alloy comprising an amorphous phase of 50% or more by volumefraction, said alloy having a composition represented by the followingformula: Cu_(100-a-b-c-d)Be_(a)(Zr_(1-x-y)Hf_(x)Ti_(y))_(b)M_(c)T_(d),wherein M represents one or more elements selected from the groupconsisting of Fe, Cr, Mn, Ni, Co, Nb, Mo, W, Sn, Al, Ta and rare-earthelements, T represents one or more elements selected from the groupconsisting of Ag, Pd, Pt and Au, a, b, c and d represent atomicpercentages which are 0<a≦20, 20≦b≦40, 0<c≦5 and 0<d≦10, and x and yrepresent atomic fractions which are 0≦x≦1 and 0≦y≦0.8.
 4. A Cu—Be basedamorphous alloy comprising an amorphous phase of 50% or more by volumefraction, said alloy having a composition represented by the followingformula: Cu_(100-a-b-c-d)Be_(a)(Zr_(1-x-y)Hf_(x)Ti_(y))_(b)M_(c)T_(d),wherein M represents one or more elements selected from the groupconsisting of Fe, Cr, Mn, Ni, Co, Nb, Mo, W, Sn, Al, Ta and rare-earthelements, T represents one or more elements selected from the groupconsisting of Ag, Pd, Pt and Au, a, b, c and d represent atomicpercentages which are 5<a≦10, 30≦b≦40, 0<c≦5 and 0<d≦10, and x and yrepresent atomic fractions which are 0<x≦1 and 0≦y≦0.8.
 5. The Cu—Bebased amorphous alloy as defined in either one of claims 1 to 4, whichhaving a supercooled liquid temperature range ΔTx of 25 K or more, saidsupercooled liquid temperature range ΔTx being represented by thefollowing formula: ΔTx=Tx-Tg, wherein Tx represents a crystallizationinitiation temperature of said alloy, and Tg represents a glasstransition temperature of said alloy.
 6. The Cu—Be based amorphous alloyas defined in either one of claims 1 to 5, which having a reduced glasstransition temperature of 0.58 or higher, said reduced glass transitiontemperature being represented by the following formula: Tg/Tm, whereinTg represents a glass transition temperature of said alloy, and Tmrepresents a melting temperature of said alloy.
 7. The Cu—Be basedamorphous alloy as defined in either one of claims 1 to 6, which iscapable of being formed into a bar or plate material which includes anamorphous phase of 90% or more by volume fraction and has a diameter orthickness of 1 mm or more, through a copper-mold casting method.